I don't know abt feeling betrayed because they barely even think abt him. Sirf once in a blue moon yaad aati hai Aparna ko ki uska koi beta bhi hai other wise she is busy with khaana, sona and others.
Meko toh pura yakeen hai ki Adi adopted hai. Won't be surprised agar kisi din usse apne adoption ke papers miljaye.
The only one who really cares abt him in that house is Imlie. Otherwise for them he is just a grumpy man.