*due to the importance of this issue, i'll make this post about Dengeki offigcial confirmation.
Dengeki officially confirmed the Marriage/Children
Bonds and Marriage
[support Conversations] After units’ bonds with one another deepen to a certain extent, units can engage in a support conversation. Upon having such a conversation, the support level increases incrementally, from C, B, A, to S, and characters’ relationships deepen in turn. Raising units’ support level from C through A is possible with any unit pair; it is useful to diligently engage in support conversations to adeptly progress through battles, as well.
[Marriage] After deepening one’s bonds through various methods, when members of the opposite sex reach the highest support level, S, the units are able to get married. Depending on the specific pair of units married, a child is born from them, and that child becomes an ally who can fight by their side.
(blazingsigurd from reddit)