What to say instead of "together with their families"?

Short answer

Say "with the blessing of their families" or "with their families' love" if you want the same warmth without the traditional phrasing. You can also simply name the people hosting, or say nothing at all and let the invitation stand alone.

If the traditional "together with their families" feels too formal, too presumptuous, or just not right for your situation, you have plenty of options. The key is to match the wording to who is actually involved and how you want to sound.

For a warmer, more modern feel, try "with the blessing of their families", "with their families' love", or "with joy and support from their families". If only one set of parents is hosting, say "with the love and support of the Smith family" or simply "with the blessing of [names]". If you and your partner are hosting yourselves, you can write "together with their children" if you have kids, or just start with the invitation line directly, for example "[Name] and [Name] invite you to celebrate their marriage".

You can also skip the family mention entirely. Many couples do. The invitation can open with your names and the request to attend. That is perfectly correct and often the clearest. If you want to acknowledge family without naming everyone, a simple "with love from both our families" works too. Just make sure the wording feels honest and comfortable to you. There is no legal requirement for this phrase, so choose what feels right.