North Korean leader Kim Jong-il put to rest this week any doubt about whom he sees as his second in command when he elevated his brother-in-law Jang Song-taek to a powerful military post, analysts said on Friday.

Kim, 67, was re-elected to his leadership post at parliament on Thursday but questions about his health, raised by a suspected stroke in August, remained. He cut a gaunt figure at the session and, his hair thinned and graying, walked with a limp onto stage.

By elevating the energetic and urbane Jang, 63, to the North's seat of power called the National Defence Commission, Kim has set him up as a kingmaker, analysts said.

Jang, an economic specialist considered pragmatic and worldly, is seen as the most likely choice to take over should Kim suddenly pass away. He could also mentor one of Kim's three known sons if he decides to groom them for succession.

When most of the people around Kim and the others on the commission will have their coffins nailed shut on them, Jang will be the one still around, said Cho Min, an expert at the Korea Institute of National Unification (KINU) in Seoul.

Jang joins a largely aging panel Kim heads. He is the youngest member of the commission, expanded to 13 men at the meeting of the rubber-stamp Supreme People's Assembly, where Kim basked in patriotic glory for a defiant rocket launch on Sunday.

The commission also took on two new men credited with the launch, widely criticized abroad as a disguised test of a long-range ballistic missile.

Jang is the husband of Kim's sister and an official in the ruling Workers' Party with an unidentified portfolio who has been seen prominently near Kim in recent months as the leader returned to public eye after the suspected stroke.

Married to Kim's younger sister Kyong-hui, Jang has walked the elite course after graduating from prestigious Kim Il Sung University and studying in Moscow, and in the 1980s starting work in the party and also getting elected to parliament.

COMPETENT AND CRUEL

Jang visited the South as part of an economic delegation in 2002.

He has not fostered strong ties with the powerful military. Some analysts say this might hurt him in a power struggle. Others contend his not being linked too closely to the military brass or ruling communist party might be seen as a bonus.

He suffered personal tragedies and career setbacks in recent years. His only child died in 2006, and he was banished from the ruling elite for a time when he was believed to have been forced into exile in 2004 as a result of a power struggle in Pyongyang.

He was seen as returning to Kim's inner circle in 2006 when he attended a reception hosted by the National Defence Commission and quickly began accompanying Kim on high-profile field guidance trips.

He is best placed, if he can stay in favor with Kim Jong-il, said Peter Beck, a professor at American University in Washington who specializes in Korean affairs.

Kim needs Jang to help him assure continuation of family rule. And he also happens to be the most competent of known family members.

Jang's role in power succession is widely expected to be as a caretaker to one of Kim's sons as he gets groomed to take over in several years, or a central player in the collective leadership after Kim's death, analysts said.

The North's nominal No.2 leader is Kim Yong-nam, 81, technically the head of state who at best does not wield anywhere near the power of Jang, analysts said.

Jang knows how to party, he can set the mood for things, and he's cruel. He's a civilian, he understands the economy but he's conservative. Kim Jong-il trusts him, Cho of KINU said.

(Additional reporting by Jon Herskovitz and Kim Junghyun; Editing by Jerry Norton)