National Organization of Mothers of Twins Clubs, Inc.
- Official site; a non-profit, nation-wide support group for parents of twins and higher order multiple birth children.
- http://www.nomotc.org/

ABC Club
- The largest German organisation for families with higher multiple birth children, from triplets onwards.
- http://www.abc-club.de/

The Association of Finnish Triplet Families
- Mostly in Finnish, but has an English section and lots of international links.
- http://www.kolumbus.fi/suomen.kolmosperheet/

Twins Plus Singapore
- Support group for parents of twins and other multiples in Singapore.
- http://www.twinsplussing.com/