FIL partner comparing children

Karin

My husbands dad has recently had a baby with his partner the baby is 3 months old now. Baby wasnt planned but that's not the point of my post. Basically they are telling us their baby is the most happiest babies and spends a lot of his time smiling is very chilled out and enjoys just sitting in his bouncer and watching baby tv. Now my little boy on the other hand is 6 months and doesn't like watching tv really. He will look for a little bit then look away. He spends most of his days moaning currently and husbands dad and partner compare the 2 of them and always say how good their baby is to ours. It gets me down a bit as theres a few months between them but I do wonder why my little one wont really watch tv sometimes. I know hes just moaning as hes teething and some days is just frustrated as he just wants to be able to get about but he cant yet. Are these normal things at 6 months?