When a galaxy fills up. And extra spots are added early in round it might be wise to hold them in reserve till you have the same amount as there are fams. Then let them join all at the same time.
Otherwise it is like playing monopoly where a few players have a quarter more dollar bills.
Or like playing risk where a few players have one more dice to throw wirh then the others.
Or just give each fam same ress at start of round and let new joiners be funded bu the fam and give them nothing but a planet to start with. And at the same time give any fam an equal amount of expos theu can build a day. Let s say 36, one player in fam he can build all 36 a day. Two players in fam each can build 18 a day and so on till four players with 9 expos to build each.
Might be some flaws in the idea as I only started to play 2 months ago.
Just think by the small number of players in each fam, one more or less makes a universe of difference.