Is it permissible to marry one's paternal aunt's daughter if the questioner was suckled by his paternal aunt's mother (his paternal grandmother), who is not his father's mother, and is it a condition to have witnesses to the suckling?

If the nursing woman explicitly states that she breastfed you five full feedings within the two years (of infancy), then according to the Hanbalis, the suckling relationship is established, and it becomes unlawful for you to marry her granddaughter, because she is considered your niece through suckling. This is based on the Prophet's (peace be upon him) saying: "What is unlawful by lineage is unlawful by suckling." As for the majority of scholars, suckling is not established by the testimony of the nursing woman alone. The Shafi'is and Hanbalis stipulate that the testimony must be detailed, mentioning the time and the number of feedings. If there is doubt about the existence of suckling or its number, then prohibition is not established.