The book Nitya Karma Puja Prakasha (Gita Press) says:
In a house, if two Shiva Lingas (linga dvayam), three Ganeshas, two conch shells (Shankha), two Suryas, three Durga Murtis (or three Shakti Murtis), two Gomati Chakras or two Shaligramas are worshiped, then that causes tension in the household.
Following is the screenshot from page 122 of the book:
Although it gives the name of the books (Acharendu, Achara Prakasha) which quote this verse but i want to know the name of the scripture. Possibly its from one of the Puranas.
BTW, the same thing is also mentioned in the Nitya Karma Puja Paddhati (Bengali) book that i have.
Q1) As per which scriptures worshiping two Shiva Lingas in one house is not considered good?
Q2) Also, what are the instructions if the number of Shiva Lingas is more than two say three or four?
Also, an additional (and optional) question:
Q3) Why is it not considered good?