Omega knowingly and repeatedly uses and manipulates the younger brother of his mate (despite knowing that they're destined), and because of "destiny" the alpha has to first deal with the heartbreak of his fated mate marrying his brother but then the constant uncertainty if the omega actually loves him or if it is just the force of destiny / convenience of his presence which reminds the omega of his brother.

Even the memories the omega shares of them doesn't seem like he actually views the younger alpha as a mate in comparison to his previous mate. I get it is framed to be cute but it just let me feeling dirty.