I think this painting is ironic because of how the couple are portrayed. The man and his sister look forlorn instead of happy or hopeful. They have a look of "life is hard." Also, the irony may be in how many parodies of this painting exist, it is very well-known. Negative meanings, family life is difficult and it is challenging just to survive the farm-life. It represents many negative feelings, and appears very straightforward and serious.