NPCs composing that spawngroup :

man_eating_creeper (100%)

NPCs spawning around that spawngroup :
(Max range : 200)

swampofnohope_42, range=135 (2620,1242,-5)

skeleton (100%)

swampofnohope_55, range=118 (2660,999,-6)

an_insatiable_nibbler (50%)
Fangor (50%)

swampofnohope_66, range=136 (2598,1243,-5)