(petitioner and brother appointed as co-executors of mother's estate and, as co-executors, transferred title in mother's residence to petitioner for $215,000; petitioner claimed FTHBC and IRS denied credit on basis that purchase was from a "related person"; court agreed, noting that while siblings are excluded from the definition of related persons under I.R.C. Sec. 36(c)(5) and Sec. 267(b)(1), the executor of an estate and a beneficiary is deemed to be a related person (See I.R.C. Sec. 36(c)(5) and Sec. 267(b)(13); home acquired by beneficiary of estate from executor of estate and substance of transaction agrees with the form of the transaction).