Consider either of these two scenarios. One, he’s finally popped the question, and presented you with his mother or grandmother’s engagement ring. Or two, you are about to pop the question to her, and you are expected to give her the unique engagement rings that has been in your family for generations. It’s a family tradition. It’s a family heirloom. Either way it’s ugly, tired, not your style, or worn through. You may want to tread carefully before immediately absconding with said heirloom engagement ring to your favorite jeweller for a makeover.
Respecting everyone’s feelings. Mother-in-laws can make formidable enemies. If it’s her ring you want to alter and she is still alive, you may want to run the idea past her first. She may also have inherited the ring and may sympathise fully. On the other hand, she may have selected it. Do your homework first.
The state of the stone and the setting. At some stage all heirloom engagement rings need repair work. Check that the stone or stones are worth saving. A worn setting is not safe for keeping stones in place. Maybe this could be your excuse for a little work. Your dream engagement ring may not look anything like the heirloom. Perhaps there could be a compromise? Perhaps you could have an eternity ring instead that meets your engagement ring dreams?
Too frail to wear on a daily basis. Worn settings and prongs will lose stones eventually. If you have to have work done, maybe it could be subtle, or not so subtle. Explain to the family member that the engagement ring needs work before starting. Too valuable to wear on a daily basis. This is a good excuse for never wearing the ring. Store it somewhere safe and only wear it to family events. Select a great wedding ring to wear instead. Too valuable to accept. This may or may not be true. If you use this excuse be leery of turning up with a ring down the track bigger and more expensive than what you returned. You would like to incorporate other family heirlooms. You have two families, perhaps there is something sentimental from the other side that should be melded in as well?