My brother have / has three children

Has, потому что brother это 3-е лицо ед.ч. у моего брата три ребёнка.

Have потомучто брат ето она для дебя он оно

Dear  anton, my summer holidays were very interesting. i spent them guess  where.i visited london! . this is really a great city with its old cathedrals, churches, palaces and museums . i took a lot of pictures of london. most of all i enjoyed going on  а river trip down the thames. we saw  the houses of parliament along the north bank of the thames. the clock tower of the houses of parliament is famous for its big hour bell known as «big ben». we saw the tower of london near tower bridge.  we also visited   the british museum and  buckingham palace where the queen lives.  we were lucky to  make a ride on the london eye wheel  and   went to  trafalgar square where  a tall nelson's coloumn stands.  i enjoyed doing the sights  very much. that's all for now. best wishes, sasha