There is a letter from the Steipler or Chazon Ish, paraphrase; a person should do hishtadlus and Hashem gives them the koach, 15 kids are not harder than one. We do not have children so they should give us nachas or support us in our old age. We are doing Hashem's ratzon, laasos nachas ruach l'Boreh Yitbarach Shemo!
Oif Simchas!