What is the ruling on masturbating out of love for one's sister, and how does one repent while returning to the sin after repentance?

"The heart's attachment to a sister is a grave reprehensible act, indicative of a diseased heart and a deviation from natural disposition. It could lead to even more serious consequences.

One must hasten to repent with sincerity and devotion, and not despair of Allah's mercy, for He loves those who repent. Repentance is accepted even if the sin is repeated.

To cure the enjoyment of incest and masturbation, one must treat the sister as a stranger as long as the heart is attached to her and temptation is feared. Thus, private seclusion with her or looking at her is not permissible."