[2] During his first two terms in the House, Castro was a member of the Liberal Party and an ally of fellow Capiznon Mar Roxas (who at that time was trade secretary and later a senator).

[6] In 2009, Castro also chaired the Capiz-based local party Ugyon Kita Capiz (UKC).

[3] The Castros also allied themselves with former agriculture undersecretary Jocelyn Bolante, who was facing allegations of plunder.

[10] In November 2013, Castro's committee unanimously approved House Bill 3587 or the Anti-Political Dynasty Act of 2013, which aims to prohibit relatives up to the second degree of consanguinity to hold or run for public offices in successive, simultaneous, or overlapping terms.

The bill proposed lethal injection for crimes such as human trafficking, plunder, treason, parricide, infanticide, rape, piracy, bribery, kidnapping, illegal detention, robbery, car theft, destructive arson, terrorism, and drug-related cases.

[15] Castro voted for the abolition of capital punishment back in 2006, but has changed his mind, explaining that he "could not accept the way crimes are being committed" in the country.

4727 with only drug-related crimes as capital offenses, in support of President Rodrigo Duterte's war on drugs.

In September 2024, ahead of his 2025 reelection bid, Castro founded the One Capiz local party.