As others have said, it's perfectly OK to cite yourself as the source for events you witnessed personally - marriage of a sibling, death of a parent, birth of a nephew, etc.
It's never ideal, though, for you to be the only source. Imagine yourself fifty years in the future, reading a WT profile where the only source for key info is a long-dead stranger's personal recollection. It's not a source anyone can review and verify, which greatly devalues it. For that reason, you should back up your personal info with documentation if at all possible. Try to work the profile as if you knew nothing about the person.