u can't choose ur relatives.....

serfspup

I love breeding sheep but they can wreck ur head.
I have a closed flock for years the only new genetics are rams and even then would use some home bred rams or from my brothers flock (have shared rams) so genetics would be similar.
would be ruthless and unsympathetic in culling would wipe out whole families without a second thought .the things that are hereditary never ceases to amaze me.
this year the temperament of my hoggets is perplexing. Considering that their dams are all sisters/cousins whose dams were sisters/cousins for generations back. they are bred out of three different rams and mated to one ram.

sire 1. is quiet and his daughters are quieter than average.
but they are rather ambivalent mothers will lick their lambs but have to make sure the lambs get a suck

sire 2. is very lively (some would say wild) and his daughters the same.
get very animated prior to lambing and would break your legs to get at their lambs, pen them up and walk away.

sire 3. was quite placid but his daughters are lively.
only a couple of these have yeaned and are ok mothers and calm down once lambed

all the same breed

I am not that bothered about the 3.group I don't have many of them and only had the sire for two seasons and will be culling them hard for other reasons.

group 2. a home bred sire and will be returning to that line as he is working in my brothers flock this year and he is breeding superbly like his father before him (who was bought for 150euro as the owner was going to factory him PBNR)

It is group 1 that worries me I have a lot of them and used him on all my best ewes for the last two years he has done exactly what I wanted and more, his lambs are very good correct and consistent (though are big at birth)
I suspect his daughters maternal instincts will improve as the get older but right now it is a pain in the ar5e.

The man in red and black

You are right that alot of things like mothering ability are heritable though often only a small percentage. No harm if you have everything else right to add this into your replacement choices.
One thing I would comment on is that you don't have a closed flock. Buying in any rams stops you being a closed flock and leaves you open to disease entry. Not being smart but it's a common thing for people who never every buy a ewe or a hogget to think they are safe from disease entry but sure buying a ram or swapping rams back and forth between farms is just as much a risk.

serfspup

very true, we try to limit the amount of rams bought in and have found homebred rams have bred well but still occassionaly need an outcross. but as u say the disease risk is a constant worry not to mention what genetic land mine that could be introduced.