Coriander, from my research is known to promote peace along those who are unable to get along, but Coriander is commonly used with love. You may add this to a love charm or spell to bring romance are use in a ritual to ease broken love affairs. However, this spell, which I know, is more of a wish spell. As Sage is commonly used for protection, one should know all of it's uses and wishing is one of them. You could write your wish on a sage leaf and place it under your pillow for three nights. If the wish is dreamt about, then it will come true. If not, you shoudl bury the leaf in the ground should no bad come to you. My best bet is to use Sage for wishing, Yarrow Flower, Chamomile, or even Roses for love like energies. If you wish to, you could also meditate, thinking of your wish while lighting Sandalwood incense, with the intention of your wish coming true, that your father will accept him, but hey, you never know. Maybe you won't need a spell or anything so your father may accept him. I think you should confront him about the matter first before you add magick into the equation.
If you need more herbal correspondences, then themagicalcat.com has an excellent herbal grimore, and I hope I was able to help.