Hi and thanks for using the forum.
Usually when babies are born with their feet in the position you described, if there is no bone abnormalities, a brace is used to correct the positioning of the feet. This is usually done for an extended time period and the feet eventually go to the normal position. Sometimes, physical therapy is done to help develop the muscles depending on the child. It would be tough to say if your ankles feeling "weak" would be related to this or if it is related to an old fracture or if it is just you. Have you tried working with a physical therapist at all? You could ask your doctor for a referral to a physical therapist who could help you establish whether or not your ankles are actually weak. They could also help you with some exercises if you need them. I hope this info helps. Good luck.
Bridget
Are you double-jointed, that is, are you extremely flexible? I come from such a family and we often start out with weak ankles and back sprains are common. As we get older we lose some of the flexibility and are less subject to these weaknesses.