When was the last time we had sex...? How can I bring back our sex life?
You must be a happy couple. Married or not married, your relationship is affectionate and stable, and there's no complaint except... frequency of sex.
These could be common reasons to leave sex far behind. In this busy society, finding the "right timing" becomes one of the most difficult things.
"Without special circumstances, if there's no sexual intercourse or sexual contact (petting, oral sex, sleeping together without garment) longer than one month, and it can be extended longer period." Japan Society of Sexual Science's definition from 1994. Generally, it is said when there's fewer than 10 times a year you can call it "sexless".
The longer the absence will be, the more difficult to act. After one month of having no sex, usually people start thinking about it. "It's been a long time having no sex..." However, you both are busy with other things then now it's two months... It's getting awkward to ask. Before it gets to the serious stage, do something about it!
You don't need to have sex only at night. How about wake-up sex? or after lunch on the weekend? Anytime he's relaxed, and awake, lock-on.
If you can wait until your partner ask for sex, there's no problem. If it's slowing down and you cannot wait anymore, perhaps it's time to change something. Express what you want in your own way. You know how to make yourself look sweet, no? And, it's okay if you let him reject you when he's not so keen. You can show your disappointment a little but DO NOT blame him.
Now you need to sort out the priorities in your life. Work, kids, hobby, and your partner. If you put a little effort in it, it's possible to find the extra time for you and your partner. It's worth it.
Think about having sex with your partner. Isn't it sometimes rather passive on your side? Not many people can be a creative sex guru, so maybe your partner isn't. But you can give it a shot? Introduce something new to your partner. Love toys, lubes, different sex positions or even fetish. Important thing is, to talk with your partner during sex. How you feel, where he likes it, try to keep communicating. Then, you will discover a new stage!
Do not rush. Do not push.
If your partner has less sex drive, too active an approach could even turn him down. When he's tired, give him a nice shoulder/back massage. "I'm sorry. I'm tired tonight... " "Don't worry. Shall I give you a massage then?" During massage, you can sneakily press his "wake-up point" on the neck, just below the hairline. If you're lucky he awakes and you can get intimate. But often, of course he will end up falling asleep. Well, then kiss him good night and sleep together. What you can get from here is, a constant skinship and his appreciation. Try to keep these two things, then the chances will be much higher.