These are the properties that I can think of with sister properties...
Legends & Samsara
Skylark & Rockhouse
Charela & Mirage
Idle Awhile Beach & Idle Awhile Cliffs

If you don't choose a hotel with a sister property or you choose not to split your stay...you can easily spend the day at Xtabi. Buy a few drinks, enjoy a meal, snorkeling & a bit of cliff jumping is available. The caves are fun to explore there also.