I don't think it's required we are all different, but I used to when I was little, but that's also because I was able to, since I have a sister to play with dolls and stuff like that, actually my sister didn't even like dolls anymore because she is older than me, so I would force her to play with me, and I would use some of her stuff sometimes and pretend to be a girl with her. even though my mom didn't want me to play dolls and such, but since she worked a lot, I would hide that from her... Actually even when I was in middle school I attempted some steps toward transition by getting earrings (I did them myself, and it was really painful lol), and getting longer hair, but then my mom would force me to cut them... ugh I wish I had a supportive mom like one of those in tv about trans children.
I mean if you actually had all brothers it's not like you can do that, but some people don't feel the need until after transitioning.