Breast feeding in public

Some people, often but not always men, are uncomfortable about breastfeeding. They find it hard to detach the idea of breasts, as a source of milk for babies, from breasts as an intimate area of the body. I presume your father-in-law would not see your bosom under other circumstances. In your own home it seems more reasonable to sit tight in the living room with everyone. Perhaps in the home of your parents-in-law you could retreat to another room.

Something else to consider is that babies themselves sometimes prefer a bit of peace. It's also good for you to focus on your baby and this is really not possible in a lively room full of people.