His paternal grandmother Concepción Borja Amador was born in Xiamen, China, to a Chinese father and a Bicolano mother from Goa, Camarines Sur.
The film, which is about typical teenage life in the 80s, also starred William Martinez, Herbert Bautista, JC Bonnin and Raymond Lauchengco.
As the majority of the target audience could relate to the story, the film was a success,[8][12] and Muhlach became a popular matinee idol.
[4] As a result of his popularity, he was cast in the title role in Miguelito, ang Batang Rebelde, in which he portrayed a rebellious teenager in conflict with his mother.
[17] Amid an emerging generation of younger actors, Muhlach took on the challenge of more mature roles, increasing his stock as one of the Philippines' top matinee idols.
[18] He was the male lead in the light-hearted chick flick films Bakit Labis Kitang Mahal (1992) and Sana Maulit Muli (1995) with leading lady Lea Salonga, Bakit Pa Kita Minahal (1994) with Kris Aquino and Ruffa Gutierrez, Basta't Kasama Kita (1995) with Dayanara Torres, May Minamahal (1993) and Ikaw Pa Rin Ang Iibigin (1998) with Aiko Melendez, and Dahil May Isang Ikaw (1999) with Regine Velasquez, as well as starring in more serious dramas: Nag-Iisang Bituin (1994) with Vilma Santos, Sinungaling Mong Puso (1992) with Gabby Concepcion, Bayarang Puso (1996) with Lorna Tolentino, and Sa Aking Mga Kamay (1996) with Christopher de Leon among others.
In 2009, he ventured into music when he participated in the all-star recording for the benefit of Typhoon Ketsana, locally known as Ondoy, titled Kaya Natin Ito!
[31] He is known for being one of the Philippine cinema's leading men of romantic dramas, being partnered up with well-known leading ladies such as Lea Salonga, Sharon Cuneta, Claudine Barretto, Maricel Soriano, Angel Locsin, Regine Velasquez, Kris Aquino, Aiko Melendez, Anne Curtis and recently Bea Alonzo and Bela Padilla.
He is also claimed as a multi-media product endorser, a role model to Filipinos of all ages, a supporter of underprivileged children, a matinee idol, and multi-award winning actor.
Lily Monteverde produced Sinungaling Mong Puso with Vilma Santos, which gained Aga Muhlach his Best Supporting Actor.
He also gained notoriety for his on and off again relationship with Janice De Belen as they starred in Pakasalan Mo Ako with co-stars John Estrada and Gabby Concepcion.
From 1990-99, he was the highest paid actor in the Philippines, paired with Aiko Melendez in May Minamahal, (1994, 1997) Kris Aquino (1993, 1994), Ruffa Gutierrez, G. Toengi (1999), Mikee Cojuangco-Jaworski (1994, 1998) Regine Velasquez, (1999, 2001, 2012) Lorna Tolentino, (1996) Carmina Villaroel, (1994, 1996) Maricel Laxa, (1994) Dawn Zulueta, (1993) beauty queen Dayanara Torres (1995) Lea Salonga, (1992, 1995) Alice Dixson and Snooky Serna (1991).
In 2002, he starred with future box office actresses Claudine Barretto in Kailangan Kita in 2002, and Dubai 2005, Sharon Cuneta in Kung Ako Na Lang Sana (2003), Kristine Hermosa in All My Life 2004, Maricel Soriano and Angelica Panganiban in A Love Story (2007) and 2008 with Anne Curtis in When Love Begins.
In 1993, he was dating Aiko Melendez during the shooting of their movie May Minamahal but after their relationship ended, he was linked romantically with Puerto Rican former Miss Universe and 1995 film Basta't Kasama Kita leading actress Dayanara Torres.
[37] Reports said Muhlach intended to follow Torres to Puerto Rico and marry her, but chose his acting career over his personal life.
In addition, he is the founder of MaAga Ang Pasko, an annual Christmas gift giving event of Jollibee starting in 1994, wherein people can donate things such as toys and clothes.
Young Critics Circle, Philippines 1996 Nominated Best Performance by Male or Female, Adult or Child, Individual or Ensemble in Leading or Supporting Role YCC Award Sana maulit muli (1995) 1994 Won Best Performance by Male or Female, Adult or Child, Individual or Ensemble in Leading or Supporting Role YCC Award Hindi kita malilimutan (1993) 1992 Won Best Performance by Male or Female, Adult or Child, Individual or Ensemble in Leading or Supporting Role YCC Award Joey Boy Munti, 15 anyos ka sa Muntilupa (1991) Box-Office Entertainment Awards (Guillermo Mendoza Memorial Scholarship Foundation) 2008 Won 38th GMMSF Box-Office Entertainment Awards Film Actor of the Year[41][42]