Synonyms of mutually

2 Syllables
jointly
3 Syllables
commonly, conjointly, agreeably
4 Syllables
concertedly, amicably, synchronously, unitedly, connectedly, harmoniously
5 Syllables
respectively, goodhumoredly, interchangeably, collectively, coincidentally, companionably, concomitantly, inseparably, reciprocally, synchronically
6 Syllables
contemporaneously, affirmatively, cooperatively