Fighting fighting

Whoever told me children would be 'partners' and play together..haiz..my 2 little angels hardly play together harmoniously wor. Po Po and Gong Gong always said 'Ur 2 girls r so difficult to take care, so nottie lei. Next time, no.3 comes along ah, more headache!'

There were many occasions of 'fighting' and just yesterday evening, when i had Tiffy sitting on one lap and Melody came up and also wanted to sit on my lap. So good lar, one on each lap...who knows, Melody slapped on her sister's head, next pinched her sister's shoulder so hard it turned red, next pinched her sister's arm and tried to push her sister away. Aiyo, while trying not to show favoritism, I still carried hugged both on my laps, erm scolded Melody (dunno whether she understands or not) and trying to soothe Tiffy cos she was crying away already. Ended up, Melody also trying to imidate her sister - also pretended to cry lor...

Hmm, was i being too lenient? Should i have punished Melody by not having her on my lap? Should i deploy the cane the next time the girls misbehaved?