It isn't necessary, I wouldn't think. On the other hand, why is it necessary for you that she have other children? You can't prove it either way from the bible alone.
Ya know, the perpetual virginity of the Theotokos has been documented since before the canonization of the bible. The very group who you trust to put the correctly inspired books in the bible also venerated Mary as a perpetual virgin AND believed in the consecrated Eucharist as the Body and Blood of Jesus Christ.
I could be wrong by a hundred years or so, but the very first time Christians started to disbelieve in the perpetual virginity of the Virgin Mary was in the last couple of hundred years or so.