In the event that the chemo therapy does not help and dies, what right will I have or my daughter to his estate?

You have no rights whatsoever. Your daughter may have rights if parentage was determined by an order of court or he signed anything acknowledging that she is his child. It also depends on his estate plan. He may have a will that leaves nothing to your daughter, or everything to her. He has the right to leave his estate to anyone he wishes, except he cannot leave out a spouse. Or he could have put everything into a trust, avoiding probate and leaving the trust estate to whom he wishes.

If he acknowledged paternity of your daughter, a child born out of wedlock, or if during his lifetime or after his death he has been adjudged to be the father of your daughter, then your daughter is an heir. If there is no will or trust then your daughter, as an heir of an intestate estate, would receive her distributive share along with any other children or other descendants. Since there is no spouse then all of the children would equally share in the estate. Descendants of a pre-deceased child of the decedent would share in the portion that would have gone to the predeceased child if alive. This applies to probate assets in the estate of the decedent. If there is a Will then the terms of the Will control as to probate assets. If there is a Trust the trust terms will control as to trust assets. Assets with designated beneficiaries (life insurance, IRA, 401K, etc) would transfer directly to the beneficiary outside of probate. If there is joint tenancy property (typically real estate) then that property would transfer immediately to the surviving joint tenant.