If he feels that tissue is the answer, I am entirely unsure of why he would want to use a homograft, when the animal tissue valves now last longer than cadaver valves. Does he not know that? Did he give any reason for choosing a homograft over a bovine or porcine tissue valve, such as a Freestyle, that encompasses both the valve and the root? Please get another opinion. If this is the same surgeon from the two previous unsuccessful surgeries, please consider a different surgeon. You could learn to like someone who can sew compromised tissue.
The anuerysm can have been formed from stress to the tissue when the first valve was placed. It's not unheard of. However, it either means he didn't have your tissue checked for connective issues when he had you open, or that he isn't overly skilled in stitching valves in borderline tissue. Neither speaks well of him for your particular case. The second valve didn't sit right, either. The appearance is that he does not have adequate (successful) experience working with myxomatous tissue. It's not a swing at him, but specific experience is a very powerful factor in dealing with this situation. The problem is that three strikes and you're out - not him.
Yeah, I know..."Tell us how you really feel, Bob..." I actually don't like the notion of shaking your faith in the surgeon. But you have to wonder if he's really the right choice for your difficult situation.
Best wishes,