Lisa, I thought you were refering to someone who wants to marry but does not want children, I was addressing that.
If you mean someone does not feel marriage is their vocation, and also does not "want" children, yes, that could be a sign of a religious vocation.
But someone who wants a relationship and wants sex, but does not want children, that is what I am talking about here.
One should be drawn to everything about a vocation: I heard somewhere that you should feel you are on the outside of it, like a candy store, pressing your nose against the window, wishing to do and experience all you see on the "inside." If that is how you feel, that is likely your vocation.
If it is marriage, that would include being with another person, intimately, sharing their everything, giving your everything, having sex, bearing/rearing children and all that entails. If you are not "drooling" over all that, then either you are not called to marriage, or if you have trouble with aspects of it (like the children part), one would need to educate themselves, and open their heart to let God show them the beauty in His will for that aspect.
If it is the religious life, it is that way of life itself, and the specific charism of the order one is considering, that allures through the glass (community life, celebrating the sacraments, celibacy, working iwth the poor, the vow of obedience, giving up one's family of origin, the life of prayer, the life of hard work, perhaps the discipline of silence, etc etc.) All that should draw you.