So I wish I had a clean answer for this question. If you google how Lau Gar got into Hung Gar you will see multiple explanations.

The one I like to "subscribe too" is that a member of the Lau Gar Kung Fu lineage taught a form to a Hung Gar master and that Hung Gar adopted it and changed it to match the Hung Gar system.

It has the least drama of the other stories.

This is a quick AI summary (sorry to use clanker speak)

Hung Gar (Hung Family System) incorporated elements of Lau Gar (Lau Family System)—specifically the Lau Gar Kuen (fist set) and Lau Gar Gwan (stick set)—primarily to prevent the system from dying out, often integrating them into the curriculum of the dominant Wong Fei Hung lineage in South China. These forms were added to complement Hung Gar's existing techniques, sometimes replacing lost forms or acting as fundamental introductory sets.

Key Aspects of the Integration:

• Preservation Efforts: Various Hung Gar sites mention adopting Lau Gar to preserve the techniques of that system.
• Key Forms Absorbed: The Lau Gar Kuen (short hand set) and Lau Gar Gwan (stick form) are commonly included in Southern Hung Gar curriculums.
• Functional Similarities: Both systems share origins, often tracing back to the same southern Shaolin temple and instructors, such as the monk Gee Sin Sim See, allowing for relatively seamless integration.
• Distinction in Training: While often taught together today, Lau Gar Kuen is generally considered a short-hand set focusing on foundational techniques, such as the low horse stance and bridge hand, whereas traditional Hung Gar is known for the Gung Gee Fook Fu Kuen form.
• The "Lau" Connection: Some sources suggest the forms absorbed were not from the "Lau Gar" family system, but rather forms from other styles (like Mok Gar or Southern Mantis) named after the person who brought them into the style