Mijn ouders zijn al wakker, maar ik lig nog in bed.

Because Dutch possessive adjectives usually do not change for number in modern standard Dutch.

• mijn ouder = my parent
• mijn ouders = my parents

So mijn stays the same whether the noun is singular or plural.

You may sometimes see mijne in older, poetic, or very formal language, but in normal modern Dutch, mijn ouders is the natural form.

Ouders means parents and is plural.

The singular is:

• ouder = parent

So:

• mijn ouder = my parent
• mijn ouders = my parents

Just like in English, the plural form is commonly used when talking about both mother and father together.

Because ouders is plural, so the verb zijn is the correct plural form of zijn = to be.

Present tense of zijn:

• ik ben = I am
• jij/u bent = you are
• hij/zij/het is = he/she/it is
• wij/jullie/zij zijn = we/you/they are

Since mijn ouders is grammatically like they, Dutch uses zijn.

Here al means already.

So:

• Mijn ouders zijn al wakker = My parents are already awake

It tells you that their being awake has happened earlier than you might expect, or earlier than the speaker’s own situation.

A useful contrast:

• al = already
• nog = still

This sentence uses both, which creates a nice contrast:

• my parents are already awake
• but I am still in bed

Here nog means still.

So:

• ik lig nog in bed = I am still in bed

It suggests that the situation continues. The speaker has not gotten out of bed yet.

Very common meanings of nog include:

• still
• yet
• another/more in some contexts

In this sentence, still is the natural meaning.

This is a very common Dutch pattern. Dutch often uses a posture verb where English simply uses to be.

Here:

• liggen = to lie
• zitten = to sit
• staan = to stand

So Dutch prefers:

• ik lig in bed = literally I am lying in bed

Even if the main point is location rather than posture, Dutch often chooses the posture verb that matches the situation.

For example:

• Het boek ligt op tafel. = The book is on the table.
• Ik zit in de tuin. = I am in the garden.
• De glazen staan in de kast. = The glasses are in the cupboard.

With bed, liggen is the normal choice because you typically lie in bed.

Because lig is the first person singular form of the verb liggen in the present tense.

Conjugation of liggen:

• ik lig
• jij ligt
• hij/zij ligt
• wij liggen
• jullie liggen
• zij liggen

So with ik, you say ik lig.

Because in bed is a fixed, very common expression meaning in bed / in the state of being in bed.

• ik lig in bed = I am in bed

If you say in het bed, you are usually talking about a specific physical bed more literally.

Compare:

• Ik lig in bed. = I’m in bed.
• De kat ligt in het bed. = The cat is lying in the bed.

So in bed is the normal idiomatic choice for a person who has not gotten up yet, is resting, sleeping, or staying in bed.

Because Dutch main clauses normally follow the verb-second rule.

That means the finite verb comes in the second main slot of the sentence.

So:

• Mijn ouders = first element
• zijn = finite verb, so it comes second
• al wakker = the rest

That gives:

• Mijn ouders zijn al wakker

Dutch word order is often more fixed than English in this respect. In a normal main clause, you usually place the conjugated verb early, in second position.

Because maar is a coordinating conjunction. After a coordinating conjunction, the next clause keeps normal main-clause word order.

So:

• maar ik lig nog in bed

Here the second clause is a normal main clause:

• ik = subject
• lig = finite verb

This is different from subordinating conjunctions such as omdat, terwijl, or als, which often send the verb to the end.

Compare:

• ..., maar ik lig nog in bed. = ..., but I am still in bed.
• ..., omdat ik nog in bed lig. = ..., because I am still in bed.

So after maar, the word order stays normal.

Yes. Wakker is an adjective meaning awake, and it is used with zijn.

So:

• wakker zijn = to be awake

Examples:

• Ik ben wakker. = I am awake.
• Ben je al wakker? = Are you awake already?
• De kinderen zijn wakker. = The children are awake.

This works much like English to be awake.

Yes, that is grammatical, but it is a bit less natural if you want to describe your physical position clearly.

• ik ben nog in bed = I am still in bed
• ik lig nog in bed = I am still lying in bed

Both are possible, but Dutch often prefers liggen with bed because it matches the physical posture. So ik lig nog in bed sounds especially natural.

It creates a neat contrast:

• al = already
• nog = still

So the sentence contrasts two situations:

• your parents have already reached the state of being awake
• you are still in bed

This kind of pairing is very common in Dutch and sounds very natural.

For example:

• Hij is al klaar, maar ik ben nog bezig. = He is already finished, but I am still busy.
• Zij eten al, maar wij koken nog. = They are already eating, but we are still cooking.