They probably feel a little lonely, especially if they are one of the few people in your friend circle with kids right now. Be a good friend and brighten their day. If you really like them, wash some dishes for them.
Also, it’s so fun to hold a baby and play with it for a couple of hours because you can always give it back to the parents. Babies smell good until they don’t, they are *usually* very cute, and all they really want is food and to take naps (relatable). What’s better than being the cool Auntie/Uncle/Unctie.
Plus, again, you can give them back.