mag ka relasyon ung 4th cousin 
sa totoo langWell, sa legal na aspeto tayo at mas advance na kumbaga basehan natin marriage (Kasi relationship ang pinaguusapan).
"Under our law, only the following marriages are considered incestuous and void from the beginning: “(1) Between ascendants and descendants of any degree; and (2) Between brothers and sisters, whether of the full or half blood” (Article 37, Family Code of the Philippines). It makes no difference whether the relationship between the parties concerned is legitimate or illegitimate as the marriage remains invalid from the very beginning if it falls under any of the mentioned marriages. (Ibid.)
Given that marriages between cousins do not fall within the aforementioned category, it cannot be concluded that such kind of marriage is invalid for being incestuous.
However, it bears stressing that such marriage may be considered void from the beginning for reasons of public policy if the collateral blood relation between the parties extend within the fourth civil degree, which essentially encompasses one’s relationship with a first cousin, aunt/uncle, nephew/niece, and sibling of a grandparent by consanguinity. This is in consonance with Article 38 of the Family Code which provides: “The following marriages shall be void from the beginning for reasons of public policy: (1) Between collateral blood relatives whether legitimate or illegitimate, up to the fourth civil degree; x x x”
Appropriately, it would be best to determine first whether your current special someone is related to you by affinity or by consanguinity. We believe that if she is related to you by affinity (non-blood related), then there is no legal hindrance for you to proceed with the marriage. However, if she is related to you by consanguinity, you need to determine your civil degree of relationship with her.
To be specific, if she is your relative by consanguinity on the 5th civil degree or farther, you can lawfully settle down with her through the contract of marriage as there is no impediment as to your blood relation. But if she is your first cousin, then we regret to inform you that you cannot lawfully marry her as such marriage is void for reasons of public policy pursuant to Article 38 of the Family Code.
--Article by The Manila Times,
Written by: Atty. Persidad Acosta
So ayun dito eh ipinagbabawal sa saligang batas ang pagpapakasal ng magkadugo hanggang 4th Civil Degree (Cousin). Whether you are legitimate or illegitimate (anak sa labas). Kung bf and gf pa lang it is considered as forbidden dahil 4th civil degree (Cousin) pa rin kayo. Unless umabot na kayo ng 5th Civil Degree (Cousin)neh legal na kayo sa batas (Pwedeng Magpakasal) kahit pa sa paningin ng kamag-anakan ninyo eh magkadugo pa kayo.
diko sure kung 4th kami ksi ang layo na tlga
PH