Sometimes, perhaps for many years, we experience strained relationships with family members and those who were once our close friends. Whether the relationship can be salvaged or not, your part in it is fully yours.
Make peace with your relatives or former friends in your heart. Let go of whatever needs to be let go, and cultivate gratitude for whatever they have contributed to you and others. Recognize your faults, without proffering excuses. Let them know, either directly or indirectly, that it is unfortunate that you are no longer close, and that you respect and love them.
That is all you can do. The other “side” of the relationship belongs to them. If you continue to contact them (perhaps on days that are significant, like birthdays and holidays), maybe they will respond in kind. But if they do not, you will have done all you could. That is all that is asked of you.