I've only ever retained one ram lamb but sold him for breeding rather than use him myself. Like you, I had his mammy, his auntie and his sister.
My plan is to buy a new ram every two years; our current one, Leo, will have his second crop of lambs this month and he'l be sold at the sales in the autumn, when I'll buy a new one. His daughters will be ready to be tupped in autumn.
I have wondered about buying a ram lamb every year, using him in November then slaughtering him (seems a bit mean) but it would save having to keep the ram and wether seperate to the ewes.