the husband's 2nd marriage is null and void.
u can file IPC 494 - private complaint
u can also get divorce on this ground, if u want.
his bigamous conduct will impose higher alimony / maintenance upon him.
u and ur son have all the lawful rights to property.
but be informed that the second son is NOT illegitimate child, though the second wife IS illegitimate wife.
there are several case laws on this.