This tutorial will help you to add, but do not replace members of the gang. Now let's proceed.
To begin with, we need to files:
peds.ide and pedgrp.dat (they are in your folder with the game /data/)
Open peds.ide using any text editor and click search
We need to first add all the same in our gang write finding FAM1(or 2, 3) we can see the line where it says here 105, FAM1, FAM1, GANG2, STAT_GANG2, gang2, 110F,1, null,5,5,PED_TYPE_GANG,VOICE_GNG_FAM1 ,VOICE_GNG_FAM2(this FAM1) copy or copy FAM2 or FAM3 lines, find the last lines of ped 288, dsher, dsher, COP, STAT_COP, swat, 1FFF, 0, null, 9,9, PED_TYPE_EMG,VOICE_EMG_RCOP1 ,VOICE_EMG_RCOP4 below it put our copied text and put him
105, FAM1, FAM1, GANG2, STAT_GANG2, gang2, 110F,1, null,5,5,PED_TYPE_GANG,VOICE_GNG_FAM1 rename it so 289, FAM4, FAM4, GANG2, STAT_GANG2, gang2, 110F,1,null,5,5,PED_TYPE_GANG,VOICE_GNG_FAM1
So add much as we want current last lines will rename in the numbers.
It remains the case for small, open the file pedgrp.dat any text editor and click search, looking for FAM, there is a line like this
FAM1, FAM2, FAM3, # Gang 2 (THE FAMILIES PLAYER GANG - AKA GROVE), add the words FAM4 looks like this FAM1, FAM2, FAM3, FAM4 # Gang 2 (THE FAMILIES PLAYER GANG - AKA GROVE), so also add much as we want, remained the last thing is to download the skin any and rename it as it should in FAM4 and shoves the gta3.img img editors.
Everything is ready. NOTE gang members may not immediately appear in the game, most importantly patience.