Ricky - am so sorry for your loss. Rest in peace little one.
Have lost four of ours in the last 2 years, the most recent of which was in September, so know only too well the despair that's engulfing you now. What I would like to say is that the inherent gift cats have is the ability to live - and love - in the moment. They never feel regret, they enjoy the day sec by second, and we can take much from that.
I know right now this grief is overwhelming. But the rest of your babies need you - right now - and as Sheila said, they draw their love direct from you. Grieve for your lost loved ones, but do them the honour of knowing their lives were not wasted or lived in vain - the loss you feel is in direct correlation to the love you shared. It's the price we all pay for loving, and it's infinitesimal in its power. Acknowledge that, shed your tears, and keep your heart open for those who still need you.