Many of us have families in different states or parts of the world. Wondering if you should invite them or if you’re obligated to pay for their flight and stay? Absolutely not. If you truly want them to share this moment with you, send them an invitation. Leave the decision up to them. Don’t assume they won’t come. They may turn it into a vacation. If they can’t make it, then they can’t.
Now if the person is a parent or grand parent, they probably will not want you to cover the expenses, but if it is in your budget, then you can pay for their flight and stay.