Li Daozong was Li Shimin's cousin.
There was no information about Li Shimin being overthrown by anyone. Therefore, I don't know who overthrew Li Shimin.
Li Shimin and Li Chengqian were father and son during the Tang Dynasty. Li Shimin was Emperor Taizong of the Tang Dynasty, and Li Chengqian was his eldest son. Li Shimin had placed great expectations on Li Chengqian and began to cultivate his talent and education when he was young. Li Chengqian had shown outstanding talent when he was young and was conferred the title of Crown Prince. He was also given special attention and love by his father. However, as time passed, Li Chengqian's behavior gradually became absurd and unruly. He indulged his interests and energy, liked hunting, and enjoyed a luxurious life. This caused Li Shimin to lose confidence in him and eventually abolished his position as Crown Prince. Li Chengqian even tried to launch a rebellion but failed. As for their specific ending and subsequent developments, the information given so far was not enough to give a clear answer.
Everyone might have different opinions. You can try to read this book and judge for yourself if it suits your taste.
Li Shimin's 24 meritorious officials included Zhangsun Wuji, Li Xiaogong, Du Ruhui, Wei Zheng, Fang Xuanling, Gao Shilian, Yuchi Jingde, Li Jing, Xiao Yu, Duan Zhixuan, Zhangsun Shunde, Liu Hongji, Qu Tutong, Yin Kaishan, Chai Shao, Zhang Liang, Hou Junji, Zhang Gongjin, Cheng Zhijie (Cheng Yaojin), Yu Shinan, Liu Zhenghui, Tang Jian, Li Shiji, and Qin Shubao.
Li Shimin had a total of 14 sons, namely Prince Li Chengqian, King of Chu Li Kuan, King of Wu Li Ke, King of Wei Li Tai, King of Qi Li You, King of Shu Li Yin, King of Jiang Li Yun, King of Yue Li Zhen, King of Gaozong Li Zhi, King of Ji Li Shen, King of Cao Li Ming, King of Jiang Li Xiao, and King of Dai Li Jian. Among them, Prince Li Chengqian, King of Chu Li Kuan, King of Wu Li Ke, King of Wei Li Tai, and a few other sons had relatively bad endings.
Li Ke was indeed favored by Li Shimin. Li Ke was very outstanding in both civil and martial arts, and was regarded as the best among the princes. Not only was he talented, but he was also skilled in archery and horse riding. Li Ke had a calm and introverted personality. After being impeached, he began to strictly restrain himself. He no longer had a record of being impeached for making mistakes. He had received the teachings of Fang Xuanling, Wei Zheng, Du Ruhui, and other great teachers, so his talent was evident. In addition, when Li Ke was young, he had fought against the Turks and made great contributions, forcing the Turkic army to retreat single-handedly. When Li Shimin was young, he had gone to the enemy's territory many times to investigate the situation. He thought that Li Ke was very similar to him and intended to pass the Tang Empire to him. Therefore, Li Ke was favored by Li Shimin.
Li Shi Min doted on Li Chengqian very much. Li Shiming's love for Li Chengqian had exceeded the normal limits, and even shocked the officials in the court. Li Shi Min ordered Li Tai to move to Martial Virtue Hall, which made the ministers feel uneasy. However, whether Li Shimin's special love for Li Chengqian was purely because he was a father's preference for his son, or because of Yuan Xiangshi's criticism, we cannot be sure. However, Li Shiming's love had spoiled Li Chengqian to a certain extent, which might have a certain negative impact on his growth. In general, Li Shimin was good to Li Chengqian, but whether he was overly fond of him required further observation and analysis.
Li Shimin's eldest son was Li Chengqian.