Here dwell, O Matali, those Asuras called Kalakhanjas who sprang from Vishnu, and those Rakshasas also called Yatudhanas who sprang from the feet of Brahman.Udyoga Narada Parva
The Devas and Asuras in the Hindu saga are actually direct descendants of Lord Vishnu.
Lord Brahma is born on a Lotus that grew from the navel of Lord Vishnu. So, Brahma is considered to be the son of Vishnu.
स पद्मकोशः सहसोदतिष्ठ-
त्कालेन कर्मप्रतिबोधनेन ।
स्वरोचिषा तत्सलिलं विशालं
विद्योतयन्नर्क इवात्मयोनिः ॥१४
With the Time that roused the karma to activity, soon from the original self [of Vishnu] with that [agitation] a lotus bud appeared that, just like a sun, illumined the vast waters with its effulgence.
तल्लोकपद्मं स उ एव विष्णुः
तस्मिन् स्वयं वेदमयो विधाता
स्वयंभुवं यं स्म वदन्ति सोऽभूत् ॥१५॥
That lotus flower of factually the universe was entered by Vishnu as the reservoir of all qualities from which He in the beginning generated the personality of Vedic wisdom, the controller of the universe [Brahma] who, so one says, was born from himself.
श्रीमद् भागवतम् स्कन्धं 3, अध्यायं 8, श्लोकं 14–15
Sreemad Bhagavatham Canto 3, Chapter 8, Verses 14–15
The first Sapta Rishis were born from Brahma and one among them was Marichi.
पुलहो नाभितो जज्ञे पुलस्त्यः कर्णयोः ऋषिः ।
अङ्गिरा मुखतोऽक्ष्णोऽत्रिर्मरीचिर्मनसोऽभवत् ।।
Pulaha generated from the navel, Pulastya from his ears, the great sage Angira from the mouth, from the eyes sage Atri came forth and sage Marichi appeared from the mind of Lord Brahma.
श्रीमद् भागवतम् स्कन्धं 3, अध्यायं 12, श्लोकं 24
Sreemad Bhagavatham Canto 3, Chapter 12, Verse 24.
Sage Kashyapa is the son of Sage Marichi.
दितिर्दाक्षायणी क्षत्तर्मारीचं कश्यपं पतिम् ।
अपत्यकामा चकमे सन्ध्यायां हृच्छयार्दिता ॥७ ॥
One evening Diti, the daughter of Daksha, in distress because of desire begged her husband Kashyapa, the son of Marichi, to father a child.
श्रीमद् भागवतम् स्कन्धं 3, अध्यायं 14, श्लोकं 7
Sreemad Bhagavatham Canto 3, Chapter 14, Verse 7
Kashyapa had multiple wives, the most prominent ones among them being Diti and Aditi.
The sons of Diti came to be known as Daityas while the sons of Aditi are renowned as Adityas.
Another of Kashyapa's wives, Danu, gave birth to another group of Asuras known as Danavas.
So all asurs, danavs etc etc are all decendant of Lord Vishnu.