{ a[$2,NR]=$0; c[$2]++ }
END {
    for( k in a ) {

       split(k,b,SUBSEP)

       t=c[b[1]] # added this bit to capture count

       if( b[1] in c && t>1 ) { # added && t>1 only print if count more than 1
         print RS "TIMES  ID" RS c[b[1]] "  " b[1] RS
         delete c[b[1]]
       }

       for(i=1;i<=NR;i++) if( a[b[1],i] ) {
          if(t>1){print a[b[1],i]} # added if(t>1) only print lines if count more than 1
          delete a[b[1],i]
       }
    }
}

abc,2,3
def,3,4
ghi,2,3
jkl,5,9
mno,3,2

Output:
TIMES  ID
2  2

abc,2,3
ghi,2,3

TIMES  ID
2  3

def,3,4
mno,3,2

END {
    for (k in a) {
        split (k,b,SUBSEP)
        if (c[b[1]] > 1) {
            if (! o[b[1]]) o[b[1]] = c[b[1]] "  " b[1] RS
            o[b[1]] = o[b[1]] RS a[k]
        }
        delete a[k]
    }
    for (q in o) print o[q] RS
}