You may be right.
Now my question is what is the meaning of marriage?
Husband and second wife always can tell that they are married in Temple(No Eveidence of marraige) or in any other place, even if they not performed any marital formalities.
what can be the proof of denyinig their marraige?. If second marriage is illegitimate in the eye of law.. then there is now question of making it either voidable or valid,,, if childern are present from such marriage , they are the strong evidence of marriage, and they will always called Biological/Natural child of their parents. rest things are just cases of law...