Tamaki "It's okay Haruhi. We've been aware of your financials from the beginning of our meeting one another remember?"
Kyoya "Yeah. We totally understand."
Tamaki "And as for why your father waited so long to tell you that you had a sibling..well there could be a number of reasons..you have no knowledge of this person right..so say the scenario of if the child he had is older than you..than your sibing might have been one he had from a previous relationship meaning you'd have an older half brother or sister, and your father just didn't tell you for one reason or another, considering you're an only child or at least had the knowledge of being the only kid in your family..or say the child is younger than you are..scenario one sense you weren't told..well there's the assumption that your parents might have separated at one time..not divorced but just separated..say they had you..but then maybe sometime after that, even though she loved him, your father's cross dressing started to make your mom uncompfortable..you know early on in their marriage..nothing against him in her opinion, or her in his opinion, it just happened..then while on the rebound he met another woman and you know, might have formed a friendship with her, just someone he could talk to, nothing to serious or at least not intended to be, and then one night just went a bit far with her..probably had conceived a child with her in the process meaning you'd have a younger half brother or sister..and then, in the case the separation lasted that long, your mom probably having tried to work things out with your father on a few occasions but never could, but they kept in contact anyway, later when your mother fell ill and she needed him back they made another effort to work things out and this time it did work, him paying child support to his other friend for their child as it was the honorable thing to do..or there's scenario two of your sibling he talked about if the child was younger..it could be a recent thing..now of course your mom is dead too so your father couldn't have possibly had conceived with her again..but there's adoption..he could have adopted a child and didn't have time to tell you due to his illness's effects occupying him most of the time.."