If you're taking this topic to that level then I'll answer the desire to have kids was given from God. He gave us opportunity to become one with our life partner and have kids. Lust is the inability to control your animalistic instincts and want to do it with everyone everywhere which is when it becomes sinful. Doing it with your loved one is not sinful,you just have to learn how to not be a slave of your flesh which takes us to gluttony, envy etc topics. Also,I'll ask you to not discuss this topic further,there are underage people here
why the west is seeing a collapse of family structure then?