Foreigners often make some strange mistakes in Chinese when they study the most difficult language--- ---Chinese. We try to analyze typical sentences to correct these errors.

        Wǒ fēicháng xǐhuān wǒ dìdì de liǎng gè nǚ'ér, wǒ cháng hé tā yìqǐ xiàqí .
False: 我非常喜欢我弟弟的两个女儿,我常和一起下棋。
        Wǒ fēicháng xǐhuān wǒ dìdì de liǎng gè nǚ'ér, wǒ cháng hé tāmen yìqǐ xiàqí.
True: 我非常喜欢我弟弟的两个女儿,我常和她们一起下棋。

“她”指弟弟的两个女儿。“两个女儿”是复数,“她”是单数,前后矛盾,应改“她”为“她们”。
她 refers to the two daughters. 两个女儿 is plural while 她 is singular. To remove the contradiction, we change 她 into 她们.