Me and my wife are more into the MFM kind of thing. She is super hot, 5 10 and beautiful. I am 5 11 toned, with 7.5 inch, so all of our 3rds were taller then me, good looking, with a cock at least my size, and more often bigger and thicker. To our disappointment all of them had erection issues, except of the first one that was not able to hold more then 5 min. The second one was flaccid most of the time, the 3rd was not able at all to perform, the 4th was better but still, was not able to keep him hard all the time. The 5th was able to hold 3 min, and the 6th was hard for 5 min. Is it something that is related to MFM? Is is something that happens also for the one that play solo? Is it something that is more common with huge cock? Any advice on the matter?