The best replacement for big sister is big brother.

The best alternatives to big sister are rated as following:
★★★★★  big brother
★★★★  big daddy
★★★  little brother
★★  little sister
  songbird

Your alternative for big sister is not listed? Suggest!
Speaking about big sister, one probably shouldn't forget about little brother.

Other search terms related to big sister and their ratings are:
★★★★★ little brother
★★★ baby brother
You have in mind a companion for big sister and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of big sister in all years. Click on graph for more.
big sister
big brother
big daddy