Why does my older brother have an opinion on the size of the house our parents want to move into?

Apparently he thinks the house they are looking at buying is too small & that his kids will find it crowded when they are all there. To which I say "too bad."

Seems like a good idea for my parents—in their mid 60s—to go ahead & downsize. And I think my mom, who has now had a knee replacement, would like to live somewhere where everything she needs is on the ground floor.