
SRMA isn't something in my breed as a problem, but if it is a known issue with a breed, and particularly as you have two litter siblings with a problem, that would be raising alarm bells with me. The problem with this sort of condition where you can't test for something, is that the condition could be there in the population as a whole, and the only time it is 'visible' is when dogs become affected by it. So the safest thing to do to avoid other dogs being affected, is avoid breeding on from lines where the condition has appeared and been diagnosed.
Prior to health testing breeders would have avoided dogs that were lame, or gone blind early, etc. And obviously as health testing has developed the results are there to show breeders where to make informed choices about whether to breed on or not. In some instances they ignore the results anyway, I've seen instances of breeding on from hips into the 40s and 2 elbow grades in my breed, and loads of instances of a dog with good results being used with a bitch where previous litters with similar lines have produced a problem. So it's not black and white, but if you know there is a health issue lurking, I'd avoid the possibility of carrying this on, and potentially producing more pups/dogs that are affected by this problem.
It's incredibly disappointing, I had it with my first girl where she came back with a 2/1 elbow grade, and the KC advice at that time was only to breed on from a 0 or 1, and she was obviously over. Added to that, the vet taking the plates mucked the first set up so badly the BVA rejected them, so there was always that niggling doubt that the plates they took may have affected the grade. At the time I had a few people telling me to carry on and breed from her, just not to show the elbow grades on adverts etc, which is just plain daft as they are there for the world to see on the KC website. Although bitterly disappointed I went with my gut instinct and stuck with the results, Indie was the most fabulous companion and definitely a one off.
It's not easy, if you can't test for a condition, but know it's 'there' in the mixture of genetics and there's evidence of it within close relatives it would make me think twice, but it's only a decision you can make personally I think, after researching what you can about the condition. The fact that it's a pretty debilitating condition as well would make me very apprehensive about breeding on I'm afraid.