If the house was deeded only to you, and your brother and sister were never added to the deed, then the money they receive from you would be a gift. An inheritance is something received via a decedent's will or estate.
By the same token, if you were the sole owner at the time the house was sold, any capital gain tax due on the sale of the house would be owed just by you. The calculation of your capital gain would depend on a number of factors (such as whether or not a life estate existed), which is why @Critter suggested you seek professional help.
Gifts to an individual that exceed $15,000 (2019) must be reported to the IRS on Form 709: https://www.irs.gov/pub/irs-pdf/f709.pdf However, no gift tax is actually due until the donor's gifts exceed the lifetime exclusion of $11.18 million. The obligation to file Form 709 rests with the donor, not the recipient. The recipient of a gift need not report it on their tax return, as a gift is not taxable income.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
