sex life

Me and my partner have always had great sex, even after our first baby we always found time to have sex and spend passionate time with each other. However, after baby number 2 things changed. We are always both so tired, he works 5 12 hour shifts a week, his 2 days off are spent looking after the boys whilst I go out to work. We hardly spend time with each other unless it's in the morning or in bed as we're going sleep. We manage to have sex once every couple of weeks, it's very quick we both just get in do our business clean up then go sleep. We are both so tired all the time. It's upsetting for me because I think about all the passionate sex we used to have and how we kissed and led up to sex. Now it's just kind off like 'do you want have sex?' Because we're both so tired to get it going we just get to the point. Does this end? Will our sex life come back once the babies have grown up? I have two boys, a 2 year old and 6 month old.