The Jealous person

Rachel envied her sister: envy is grieving at the good of another, than which no sin is more hateful to God, or more hurtful to our neighbours and ourselves. She considered not that God made the difference, and that in other things she had the advantage. Let us carefully watch against all the risings and workings of this passion in our minds. Let not our eye be evil towards any of our fellow-servants, because our Master's is good. Jacob loved Rachel, and therefore reproved her for what she said amiss. Faithful reproofs show true affection. God may be to us instead of any creature; but it is sin and folly to place any creature in God's stead, and to place that confidence in any creature, which should be placed in God only. At the persuasion of Rachel, Jacob took Bilhah her handmaid to wife, that, according to the usage of those times, her children might be owned as her mistress's children. Had not Rachel's heart been influenced by evil passions, she would have thought her sister's children nearer to her, and more entitled to her care than Bilhah's. But children whom she had a right to rule, were more desirable to her than children she had more reason to love. As an early instance of her power over these children, she takes pleasure in giving them names that carry in them marks of rivalry with her sister. See what roots of bitterness envy and strife are, and what mischief they make among relations. At the persuasion of Leah, Jacob took Zilpah her handmaid to wife also. See the power of jealousy and admire the wisdom of the Divine appointment, which joins together one man and one woman only; for God has called us to peace and purity.
I need to say this. God does not want man to have two wives but He records history. You see the problem when a man have more than one wife. If you don't want problems, listen to the Bible.

Genesis 30:1-13

 When Rachel saw that she was not bearing Jacob any children, she became jealous of her sister. So she said to Jacob, “Give me children, or I’ll die!”

² Jacob became angry with her and said, “Am I in the place of God, who has kept you from having children?”
³ Then she said, “Here is Bilhah, my servant. Sleep with her so that she can bear children for me and I too can build a family through her.”
⁴ So she gave him her servant Bilhah as a wife. Jacob slept with her, ⁵ and she became pregnant and bore him a son. ⁶ Then Rachel said, “God has vindicated me; he has listened to my plea and given me a son.” Because of this she named him Dan.^[a]
7 Rachel’s servant Bilhah conceived again and bore Jacob a second son. ⁸ Then Rachel said, “I have had a great struggle with my sister, and I have won.” So she named him Naphtali.^[b]
9 When Leah saw that she had stopped having children, she took her servant Zilpah and gave her to Jacob as a wife. ¹⁰ Leah’s servant Zilpah bore Jacob a son. ¹¹ Then Leah said, “What good fortune!”^[c] So she named him Gad.^[d]
12 Leah’s servant Zilpah bore Jacob a second son. ¹³ Then Leah said, “How happy I am! The women will call me happy.” So she named him Asher.