How do the departed souls get the food given by their siblings?

Question

How do the departed souls get the food given by their siblings?

Answer 1

Summary- Though the gross offerings remain here, the essence of these offerings is delivered to the departed ancestors. The ones who carry the offering to them are called the Pitr devatas and the departed ancestors are located by the help of the name, gotra and mantra. Thus the essence of the shraddha offering is delivered to them by the Pitr devatas.

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Detailed As discussed about who has the right to do Shraadha, siblings of the same gotra are included and the process is the same.

The same question as raised by you, was raised by King Karandhama (Skanda Purāṇa) to Mahakala (Bhagwan Shankara) and also by Garuda to Bhagwan Shri Hari (Garuda Purāṇa). For this, we shall understand:

1. What part of the offerings do the ancestors actually consume, since everything remains on earth?
2. How do the ancestors get what they consume (as stated in Point 1) or who takes it to them?

1. What offering do the ancestors actually consume?

First let us see how the shraadha pinda and tarpana reaches the ancestors despite remaining on earth. This has been explained by Mahakala in the Skanda Purana, Maheśvara khaṇḍa Kaumārikā khaṇḍa Chapter 40.

King Karandhama asks Mahakala a valid doubt about how the offering to the forefathers reaches them, despite everything remaining on earth itself:

139b-143 O Holy Lord, this doubt perpetually haunts my mind. Tarpana is performed by men. The water (offered) goes into the water, but how do the ancestors become delighted and contented thereby? In this manner, the offering of rice balls (pinda) etc. and the worship everything is observed only here. How can we presume (think) that it is enjoyed by Pitṛs and others?

Mahakala explains how the Pitrs accept the subtle essence of the offering. His reply is as follows:

The form of existence of those Pitṛs and the heaven-dwellers is of this nature. They can be talked to from afar; they can be worshipped also from afar and they can as well be eulogised from a distance. Their body consists of nine principles, viz. the five Tanmātras (subtle elements of sound etc.), the manas, buddhi, ahankara and the Jada (i.e. Prakriti). Purusha is considered to be the tenth one. Therefore, they are satisfied with the subtle essence of smell, taste and sound. They take the essence of touch. They are contented on seeing a pure and clean thing. Just as grass unto animals and food-grains unto human beings, so also the subtle essence of foodstuff forms the diet of the species of deities. Hence they take up the essences of the principles. The rest is seen here itself.
-(verses 144-149)

In the Garuda Purāṇa Dharma Kāṇḍa, Preta Kalpa Chapter 10, Bhagwan Shri Hari also explains not only about how the ancestors being in the above subtle form obtain their offering, but also ancestors who’ve moved on according to their karma in other yonis. He says:

Oh king of birds listen how the Shraddha offering grants satisfaction to the departed. If as per his Karmas he has become a Deva, the offering is received by him in the form of Amrita. In the Gandharva or Yaksha yoni he receives it as Bhoga and as cattle he receives it as grass. The same Shraadha offering is obtained in the form of air to one of a Naga yoni, as fruits for a bird, for Rakshasas as Amisha food. For Danavas as meat, for Preta as blood and for Hunans as food and water.
-(verses 4-7)

2. How does the Offering reach them?

The first part explains what part of the offerings goes to them and also that it does reach them despite being in different Yonis. Since we are certain that offering reaches them, the question arises as to how?

Quoting from the Garuda Purāṇa, Dharma Kāṇḍa, Preta Kalpa Chapter 10.

Bhagwan Shri Vishnu explains the importance of mentioning the name and gotra of the pitr. The name and gotra acts as a sort of address, that the offering has to be delivered to, by the carriers. He says:

Oh Garuda, the proof of the Shruti is strong and akin to nectar. In a Shraaddha, the name and gotra of the departed is the facilitator of the offering (Kavya) as also the mantras recited with devotion. You should not have any doubt in the matter as regards how these mantras facilitate the delivery of offerings.

As discussed in my answer there are 7 Pitrs who are called the Pitr devatas or Deva Pitrs. Each has some role to play, especially Kavyavahana who’s role is to carry offerings (Kavya) to the pitrs.

While referring to these Pitrs, Bhagawan Vishnu then explains that when the Name and Gotra are recited, it is these Pitrs (especially Kavyavaha) who carry the essence (as discussed in Point 1) of the offering to the correct address I.e. to the correct Pitr. He says:

To understand better I will tell you about another. Agnisvatta and others are the chief of the Pitrs. When the time comes, then offerings given by proper rituals are delivered to the Pitrs. Wherever the departed jiva is, there these Agnisvatta and other Pitr devas take the offering as facilitated by the Name, Gotra and mantra. Among hundreds of Yonis, in whichever one the jiva might be, the name gotra and mantra gives him satisfaction. Whatever food they might be eating in that yoni, the food reaches them in that very form. Even the Vishvedevas accept the offering and satisfy the Pitrs.
-(between verses 10-20 I’ve skipped some)

Shri Hari also explains during a Brahmin bhojana the Pitrs come in the form of air, enter the Brahmins bodies and eat along with them.

3. Conclusion

From the above explanations it’s clear that the offerings in gross form remain here, but their subtle elements reaches the Pitrs in the form of food which they eat in whichever yoni they’re in. The job of carrying the essence of offerings is done by the Pitr devatas, especially Kavyavahana.

Thus, the departed ancestors get the essence of whatever is offered to them (by the ones who have the right, including sibling) which is delivered by the Pitr devatas, being facilitated by the name, gotra and mantra recited during the rituals.