In construing this subsection, a power in the decedent to withdraw income or principal, or a power in any person whose interest is not adverse to the decedent to distribute to or use for the benefit of the decedent any income or principal, shall be deemed to be a power in the decedent to withdraw so much of the income or principal as is subject to such power, even though such income or principal may be distributed only for support or other particular purpose or only in limited periodic amounts.
20 Pa.C.S. § 2203