Technically, you won't increase the population of Japan unless you have at least three kids. Synergy, you know. After all, you and your lair mate are only mortal, so unless you leave behind one more person than two, the population will stay the same. So, I'd have one more child. Moreover, more children both increases survivability and the chance of passing on the best of yourselves, physically as well as memetically speaking. It just doesn't make any sense on any level to arbitrarily limit your generation of life. More life means more production of goods and more chance of intellectual achievement. Then competition results in the best possible human beings getting to the top, and better people make the world a better place. Ergo, you and your mate ought to aim for glory, not temporary convenience, as if you had the foresight to plan perfection. No one does. No one can. Nature is what it is. You can only have natural pride and try to make your bloodline better and more extensive than everyone else's. Anything less is subhuman and degenerate. Priorities, man! We are not here for sentiment, but for power. Don't you want your flesh and blood to see the end of time?
Anyhow, welcome back.