Welcome to LDW! The games are super addicting (I should know: I own them all. :P)

I sounds to me like you are doing everything correctly. Make sure they have food, are happy and healthy. If you have purchased the doc consult and used baby boost when recommended, there is not much else you can do. Keep trying. If they say it is too soon, you can wait about 15 minutes and try again. If they argue, just keep dropping them onto one another until they try. The oldest I have been able to successfully have a baby is 50 (for the mother.)

Other than that, my theory is that some couples are just more "compatible" than others. I have had more than one multiple birth in the same family and had difficulty with conception in the same family repeatedly. It seems the ones who argue are the ones who have the most trouble conceiving. (But that it just my observation and I have not actually collected stats on it to see if it is fact.) So, if you have an unlucky couple, just know that you have many more generations to come. You will get twins and triplets one day. Just stick with it!